What Should I Buy for my New Growroom?

So in a couple of months I'll be moving into a place with a nice walk-in closet, which I of course will be using as my new growroom. It's about 6ft wide x 5ft deep. I just got a new job and I'm not pressed for cash so I think I'm going to use my entire first paycheck (about $500) toward my new hobby. So I ask all of you, what should I get?

Right now I use fluoros for everything, so I'm obviously going to buy an HPS for flowering. I'll still use my T5 system for veg though because it's amazing and cheap on the electric bill. I'm also going to get a pH meter because I'm tired of using these gay pH strips that probably don't do me a whole lot of good. So that's about $200 gone.

I should probably get a nice ventilation system now that I'm going to use HPS, but I don't know what I would need. Anything else you guys would suggest for the remaining $300?

what are you going to be growin..hydro dwc, aero soil?

I'll be growing in soil.

im in the same situation as you man..getting a new job and not affraid to throw down on a project, personally im going to try dwc because of the fast growth. your pretty much set for the soil grow tho..the only thing i suggest is security if u dont have it already

maybe some mylar, some really good nutes (if you don't have 'em already), and how bout a variety of seeds... it'd probably be nice to be able to grow a couple differnet things if you feel like it...

and we all forgot co2

maybe put in 100 bucks at target or kmart or someplace like that for a little 5000 btu window air conditioner to make sure your temps are always low... very important with that hps your upgrading to...

A good thermometer

not just a thermometer... maybe a climate control system... something that can trigger an airconditioning unit, or ventalation, a dehumidifier (or humidifier depending on how your grow room is)

or... actually with that much space if you get just one 400w hps get a light mover too, you can cover more area and not have to worry about hot spots and whatnot... i think this would be a wise choice if you want to maximize your lighting

Carbon filter and fan. You will not have to worry about odor and you get the double plus of ensuring good ventilation. If you find a good deal on that, you might also have enough for a temporary replacement door and cheap dryer venting so you can get good circulation.

Actually, a closet can be the hardest place to have a grow.
You mentioned using HID lighting, and as such, your first order is going to be ventilation. Plan ahead, and get more than you think you'll need.
Some of this depends on where you live and the ambient temps.
Obviously Alaska is going to have different needs than someone in Florida.

My grow room only has a 430 watt light, and I am pushing 750 cfm using two inline fans, my temps are usually at about 83 on a hot day.
You can see how good ventilation can be a real problem.
Peace